Aircraft wing connection



ugfS, 1947. l A, J, KLOSE 2,425,099 A l AIRCRAFT WING coNNEcTloN Filed Nov. so, 1944 l B2b ,17 /13 C 1o 2o I J WWW.'

' INVETOR.

'f mamy Patented Aug. 5, 1947 AIRCRAFT WING CONNECTION Alfred J. Klose, Rolling Hills, Calif., assgnor to Consolidated Vultee Aircraft Corporation, a corporation of Delaware `Application November 30, 1944, Serial No. 565,819

7 Claims.

The present invention relates to improvements in connections and joints and more particularly to improved means for effecting a junction between such major components of an aircraft structure as the outer and inner wing panels.

In the manufacture of aircraft it is customary to construct the wing in a plurality of sections, with a stub wing or center section forming the inner wing panel to which is attached the outer or main wing panels. To facilitate servicing, repair and replacement, the outer wing panels are usually releasably attached to the inner or fuselage sections, these attachments including major structural connections through which the wing Other advantages and objects will become apparent to those skilled in the art after reading the present description taken together with the accompanying drawings forming a part hereof in which:

Fig. 1 is a top plan view of a fitting embodying the present invention in which the adjacent structure is shown fragmentarily;

Fig. 2 is a partly cross-sectioned side elevational view of the tting and structure shown in Fig. 1;

Fig. 3 is an end elevational view of the same;

Fig. 4 is an enlarged detail View of the taper threaded portion-of the tting shown in the previloads are transmitted into and across the fuselage l5 ous figures; and during flight. As heretofore constructed they Fig. 5 is a cross sectional view, to a reduced also include a plurality of secondary flange stiifscale, as taken along the lines 5-5 of Fig. 1. ener and cap strip connections primarily for the Referring now to Figs. 1 and 2 the right side purpose of joining and aligning the sections and of each of these gures represents structure asso- .fairing the joints between the skin covering of elated with the outer wing panel and the structhe two adjacent panels or sections. ture of the left half represents that portion in- 'I'he design and construction of the structural side of the inner bulkhead which is connected joints between the outer and inner wing panels to the fuselage or inner wing section. These lghas heretofore presented many problems in order ures are taken as viewed looking rearwardly, or to provide a joint connection which would he toward the tail of the airplane, and from the plan as light as possible in weight, and which would not view of Fig. 1 it will be noted that the main wing be too complex due to the necessity of including spar or beam IIJ is swept forwardly'` as indicated external straps, splices, boltheads and other proby the angle made by the spar axis C`B with jections which frequently interfered with adjarespect to the normal spanwise axis A-C, longicent parts and structure. Amajor cause of structudinally of the wing span. A forwardly swept tural failures in prior wing-to-fuselage connecspar has been selected for illustrative purposes tions has resulted from unequal distribution and only and it will be appreciated that the invention high concentration of stresses in transferring the is equally applicable to longitudinally aligned or loads between the fuselage and the outer wing rearwardly swept spars, or to wings in which there panels. These disadvantages and objections have is a change in dihedral at the wing-to-fuselage been largely overcome and eliminated by the presjoint. It will also be understood that the spar ent invention comprising an improved tapered Id may be comprised of upper and lower spar cap thread fitting of simple economical construction or chord sections II of which only the upper having a high strength-to-weight ratio, which is chordal element is shown in the drawings, these easily installed and occupies relatively little space. 40 chord sections either being the same or varying It is accordinglya major object of the present in accordance with the strength characteristics of invention to provide an improved structural joint the material used and the loads to which they are or connection particularly adapted for effecting subjected. the junction :between the major components of The spar or beam IIJ is preferably formed of a an aircraft structure. Another object is the proflanged extruded section of Duraluminum, or vision of a fitting for such a connection which is other aluminum alloy or structural material, havrelatively simple and economical of construcing laterally and downwardlyextending flanges I4 tion and highly efficient in its gradual load transadapted to receive and be riveted to the skin covferring characteristics. It is a further object to ering sheets I3 and the web plate I2 as by the rivprovide such a joint in which the connection is ets I5, The inner margin of the outer wing panel readily made or detached by means of a fitting is dened by a transverse bulkhead I6 comprising which is adequate in strength, while light in a web plate which is anged at the top and botweight, and occupies relatively little space thereby tom as at I I to receive the skin I3 by suitable obviating interference with adjacent parts or rivets, or other fastenings. The bulkhead and its structure. flanges are interrupted at the spar fitting connections to permit the extended portions I2a and I2b of the spar web I2 to extend therethrough and are stiffened adjacent the spar web by means of the vertical stiifener angles I8. The upper and lower iianges I'I of the bulkhead plate I6 are additionally reinforced by the similarly interrupted flange angles I9. The extended portion I2b forms upwardly and downwardly extending apertured ear or lug portions and are stiiened by the additional channel structure indicated at I2c.

A tting 20 of eicient form and function serves to transmit the load from the spar chord II through the bulkhead I 6 to the fuselage eye iitting portion 22, as well as to serve as a tie or splice between the interrupted portions of the bulkhead I6. This tting 2U is comprised essentially of a taper threaded conical or male section 2| adapted to be threaded into mating female socket or opening IIa in the spar chord Il, an oppositely extending bifurcated fuselage tting 22, and intermediate transversely extending flange or ear portions 23 and 24. The tapered conic joint between the threaded portions IIa and 22| comprises an essential portion of the present invention in that it provides a highly eflicient means for utilizing to the fullest extent the inherent mechanical advantage of a gradual load transfer. The fitting 2Q is preferably formed and machined from chrome molybdenum steel with its conic portion 2I tapered and threaded for its entire length with a single 60 degree sharp V thread. The crosssection of a thread, which has been found satisfactory, is shown in detail in Fig. 4 in which the threads are cut symetrically or 30 degrees on each side about the transverse axis E-D normal to the axis of the conic portion C-B. The sharp V formed at the top and bottom of the threads is preferably iiattened or truncated at the conic surfaces which are formed by the ridge and root portions as indicated at 25 and 25.

The allowable tensile stress of the chrome molybdenum steel fitting, as compared to that of the Duraluminum cap element into which it threadingfly mates, varies in a ratio of approximately three to one in favor of the steel tting in the case of the materials which have been selected for this description. The threaded conic portion EI is provided with an internal bore or cylindrical recess or core 2l in view of the higher allowable stress of this portion; and the diameter of this bore, the end diameters or taper of the threaded portions and the cross-section of the spar chord can be so proportioned that the load is transferred from `the spar chord I I to the conic portion 2l, or vice versa, in a predetermined and gradual transfer. In engaging the cone portion I with the threaded socket the starting point of the thread is not critical inasmuch as the steel cone plug can be forced into the Duraluminum chord socket several turns after the parts are screwed together hand tight. The number of turns necessary to make up or release the threaded joint depends upon the taper of the cone plug, and the pitch and depth of the thread. The taper shown in the drawings is approximately 3 inches per foot and the plug can be maintained in the attached relationship without the use of a locking device.

The load in being transferred from the wing beam cap member il into the fitting 20 is relatively light at the small end of the tting taper, increasing in proportion as the cross-sectional area of the taper increases, until the fitting is carrying the entire load. This applies equally to the gradual decrease in load within the spar chord, decreasing in proportion as its cross-sectional area is reduced due to `the increase in diameter of its tapered socket portion. The desirable loading characteristics described permits a saving in weight by the use ci this tapered tting of from 40 to 50 per cent over the bolted strap or bolted ange connections heretofore utilized for such wing spar connections, and reduces to an extreme minimum the amount of metal it is necessary to remove from the spar cap member in order to accommodate the tapered fitting.

The wing load which is transmitted from the spar chord II to the conic tapered portion 2| of the tting 2D is transferred through its bifurcated or clevis portion 22 to a suitable clevis or other apertured or eye connection (not shown) as by means of a pin engaging the bore 29. The eye portion 2. is slotted as at 2S' to receive the abovementioned ear or lug portion i211 which is also apertured to receive the pin engaging the bore 2S. cross-section adjacent its central portion at C being substantially conic in its form outwardly from the point C to the region of the beginning ci the slot 28, at which the sides 22a and top and bottom 2213 are faced 01T to provide a substantially square or rectangular section. The bore Z3 of the eye connection at E2 may alternatively serve to receive a hinge pin for use in a folding wing airplane.

1n the region of the central point C the two horizontal or laterally extending flange or lug portions 23 and 2li extend such that their outer faces come within the vertical plane formed by the inner surface of the bulkhead web i5, to which it is bolted or riveted through the holes 23a and Elia, respectively. The framing connection assembly is accomplished by first threading the cone plug into the chord socket and after it has been tightened and aligned the spar is assembled and the bulkhead IG-Il-I-le brought into position and fastened to the spar and the ears 23 and of the fitting l'n assembling the spar its web l2, continuing past the bulkhead IS as at I2a and ib, has the latter portion extended between the bifurcations 2S in the eye portion 22 and serves to Yprevent application of bending loads upon the fitting.

It will accordingly be noted that a compact fitting of relatively high strength-to-weigh ratio is provided to transfer in a gradual and highly eiiicient manner the loads within the spar chords to the fuselage tting while at the saine time its laterally extending portions serve to stiffer; and tie together the portions of the bulkheads which are interrupted by the insertion of the tting. It will also be noted that the junction between these major components of the aircraft structure is effected without the necessity of external straps, splices, bulkheads or other projections resulting in a relatively clean design which eliminates to a great extent the possibility of interference with nearby parts of the struct .ra Other forms and modifications of the present invention both with respect to its general arrangement and specific details, as may occur to those skilled in the art after reading the present speciiication, are intended to come within the scope of this invention as more particularly dened in the appended claims.

I claim:

1. 1n aircraft construction; a wing having inner and outer wing panels; said outer panel including a spanwise extending spar chord element having a conic threaded portion therein; and a uni- The eye portion 22 is of generally circular.

tary wing spar fitting for joining said panels cornprising a correspondingly threaded conic portion engaging the conic threaded portion of said spar chord element and an apertured portion adapted to be connected to said inner wing panel.

2. In aircraft construction, an inner Wing panel,

an outer Wing panel having a spar chord, a conic threaded socket longitudinally disposed at the inner end of said outer Wing spar chord and connecting means having a conic threaded portion engageable with said socket portion and an oppositely disposed clevis adapted for the connection of said outer wing panel to said inner Wing panel.

3. In a structural joint for aircraft; an aircraft supporting structure; an aircraft component contiguously disposed with respect to said supporting structure; said aircraft component having a longitudinal chordal element and a transverse bulkhead element; said chordal element having a conic threaded socket portion; and a unitary tting for connecting said aircraft component to said supporting structure including a threaded conic male portion engageable with said threaded conic socket portion of said chordal element and further connecting means carried by said tting at an opposed portion thereof with respect to said conic male portion on the opposite side of said bulkhead element for attachment to said supporting structure.

4. A structural joint for connecting an aircraft component including a longitudinal spar chord element and a transverse bulkhead element to a supporting structure, comprising a unitary itting comprising a conic threaded portion axially engageable with a mating conic recess in said spar chord element, said fitting being apertured at an opposed terminal for attachment to a supporting structure, and flange elements projecting from an intermediate portion of said fitting for attachment to said bulkhead.

5. A structural joint for connecting an aircraft component to a supporting structure, said aircraft component including a longitudinal spar member and a transverse bulkhead member, said spar member including upper and lower longitudinal chord elements, said bulkhead member including a transversely extending web plate, and connection means comprising a threaded conic portion longitudinally engaging with a mating threaded socket in one of said spar chord elements, said connection means having integral laterally extending lug portions for attachment to the web plate of said bulkhead member and an apertured portion provided on said connection means for the attachment of said component to a supporting structure.

6. In aircraft wing construction comprising inner and outer wing assemblies, said outer wing assembly including a longitudinally extending spar having a co-eXtending chord element and a transverse bulkhead, means for detachably connecting said inner and outer Wing panels comprising a joint fitting having a conic threaded male portion engageable with a threaded socket portion at the inner terminal of said outer Wing spar chord, said joint tting having an inner bifurcated portion for attachment to said inner Wing assembly and flanged portions projecting from an intermediate portion of said joint fitting adapted for attachment to said transverse bulkhead.

7. In aircraft construction; a fuselage section; an outer wing panel disposed outboard of said fuselage section; said outer Wing panel including a spar chord of a material having a given allowable stress; a threaded conic socket in said spar chord; a unitary fitting for the attachment of said outer `wing panel to said fuselage section; a conic threaded attachment portion on said fitting engageable with said threaded socket in said spar chord; the said attachment portion of said fitting being of a material of appreciably greater allowable stress than said spar chord material, and the taper of said threaded conic attachment portions being proportioned to permit a gradual load transfer between said outer wing panel spar chord and said unitary attachment fitting.

ALFRED J. KLOSE.

REFERENCES CITED The following references are of record in the nie of this patent:

UNITED STATES PATENTS Number Name Date 2,347,542 Cyron et al. Apr. 25, 1944 1,167,943 Short et a1 Jan. 11, 1916 1,403,553 Horn Jan. 1'7, 1922 1,908,838 Green et al May 16, 1933 

